This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. A long-term objective of ACERT in the study of motional dynamics has been to combine the complementary relaxation information obtained from multi-frequency ESR studies of lineshapes and NMR spin-relaxation, in particular the frequency-dependent NMR Dispersion method NMRD. This project, with groups in Poland and Sweden, is to a combined study on ESR and NMRD on solutions of transition metal ion complexes. Initial work is on Gd(III) complexes used as contrast agents in MRI in order to better understand their properties, and to verify the applicability of the commonly used pseudorotational model of transient zero field splitting (ZFS). According to this model the transient ZFS is described by a tensor of a constant amplitude, defined in its own principal axes systems, which changes its orientation with respect to the laboratory frame according to an isotropic diffusion equation with a characteristic time constant (correlation time) reflecting the time scale of the distortional motion.